For people wanting to use hashtags to allow people to find their posts, I checked recent tags for art/photography related posts to check frequently. Including one of the ones that are getting more use will help people find you.
Tags with recent posts:
#photography 16
#cosophoto 1
#art 5
#cosoart 7
Tags with no recent posts. You might also want to include one of the ones above to be found:
photo
images
photographylovers
photographyisart
painting
paintinginparadise
paintinginprogress
paintingisabighellno
paintingminiatures
cosoimages
cosophotography
cosophotochallenge
paint
painted
paintedladies
cosopainters
cosopainting
cosopaintings
cosopaints
art_is_culture
artagainstdeforestation
artappreciation
artasprotest
cosoartafterdark
cosoartappreciation
cosoartcollective
cosoartfractals
*internally debates with self whether to tag everything with "paintedladies" from now on*
Also, if you post a lot of art/photos where the visual is the whole post, consider that we have at least one blind user who may chose to filter posts with a tag rather than mute you altogether.